Selective alkaline leaching of antimony from Low-grade refractory gold ores and process optimization

Abstract

To eliminate the adverse effect of antimony on extracting of gold in matte smelting process from Sb-bearing refractory gold ores, the sodium sulfide leaching method was proposed to selectively remove antimony in advance. On the basis of the analysis and characterization of raw materials (XRD, SEM-EDS, mineralogical phase analysis, etc.), it can be detected that the antimony in refractory gold ores is mainly in form of stibnite with small quantities of oxides, and the gold is mainly wrapped up in sulfides and silicates. The effects of sodium sulfide and sodium hydroxide concentration, temperature, leaching time and liquid–solid ratio on the extraction rate of antimony and gold were discussed. Furthermore, the response surface method was applied to distinguish the interaction influence of process parameters on the antimony and gold extraction rate. It is detected that the polysulfides and thiosulfates are the main cause of associated leaching of gold. Furthermore, the regression equation model is established adopting the antimony extraction rate as response value, and it can be deduced that the relevance degree is Na2S concentration > temperature > NaOH concentration. Accordingly, the optimized process results are determined as follows: the extraction rates of antimony and gold reach 94.15% and 3.37%, respectively, under Na2S concentration of 85.66 g/L, NaOH concentration of 45.5 g/L, liquid–solid ratio of 1.5, leaching at 90 °C for 5 min, which are very consistent with the predicted values of the regression equation, proving the feasibility of the proposed optimization model.